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  2. Nitrogen cycle - Wikipedia

    en.wikipedia.org/wiki/Nitrogen_cycle

    In addition, humans have significantly contributed to the transfer of nitrogen trace gases from Earth to the atmosphere and from the land to aquatic systems. Human alterations to the global nitrogen cycle are most intense in developed countries and in Asia, where vehicle emissions and industrial agriculture are highest. [46]

  3. Human impact on the nitrogen cycle - Wikipedia

    en.wikipedia.org/wiki/Human_impact_on_the...

    Human activities account for over one-third of N 2 O emissions, most of which are due to the agricultural sector. [2] This article is intended to give a brief review of the history of anthropogenic N inputs, and reported impacts of nitrogen inputs on selected terrestrial and aquatic ecosystems.

  4. Marine biogeochemical cycles - Wikipedia

    en.wikipedia.org/wiki/Marine_biogeochemical_cycles

    The nitrogen cycle is as important in the ocean as it is on land. While the overall cycle is similar in both cases, there are different players and modes of transfer for nitrogen in the ocean. [81] Nitrogen enters the ocean through precipitation, runoff, or as N 2 from the atmosphere.

  5. Nitrogen fixation - Wikipedia

    en.wikipedia.org/wiki/Nitrogen_fixation

    Nitrogen fixation is a chemical process by which molecular dinitrogen (N 2) is converted into ammonia (NH 3). [1] It occurs both biologically and abiologically in chemical industries. Biological nitrogen fixation or diazotrophy is catalyzed by enzymes called nitrogenases. [2]

  6. Nitrogen assimilation - Wikipedia

    en.wikipedia.org/wiki/Nitrogen_assimilation

    Nitrogen assimilation is the formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment. Organisms like plants, fungi and certain bacteria that can fix nitrogen gas (N 2) depend on the ability to assimilate nitrate or ammonia for their needs. Other organisms, like animals, depend ...

  7. Denitrification - Wikipedia

    en.wikipedia.org/wiki/Denitrification

    The lighter isotope of nitrogen, 14 N, is preferred during denitrification, leaving the heavier nitrogen isotope, 15 N, in the residual matter. This selectivity leads to the enrichment of 14 N in the biomass compared to 15 N. [ 27 ] Moreover, the relative abundance of 14 N can be analyzed to distinguish denitrification apart from other ...

  8. Biogeochemical cycle - Wikipedia

    en.wikipedia.org/wiki/Biogeochemical_cycle

    A biogeochemical cycle, or more generally a cycle of matter, [1] is the movement and transformation of chemical elements and compounds between living organisms, the atmosphere, and the Earth's crust. Major biogeochemical cycles include the carbon cycle, the nitrogen cycle and the water cycle. In each cycle, the chemical element or molecule is ...

  9. Nitrogen - Wikipedia

    en.wikipedia.org/wiki/Nitrogen

    The human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes the movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere.